What Causes Cause Empires To Failure?

The economic/ecological collapse, internal rebellion and the external invasion are the three reasons that cause empires to fail. Let us talk about the Assyrian empire, specifically how these three factors contributed to collapse or decline of this empire. For the first and second Assyrian empire, out of these three important reasons; internal rebellion and the external Invasion were the important reasons. The Assyrian empire was a small city state and they were selling timbers to their neighboring empire (Babylon) thus getting a lot amount of money which means they really did not have an economic problem. The problem was that it was a small city state and did not have much population of people to control that empire and the large influential